In such an eccentric screw pump, the rotor is normally connected to the drive or drive shaft by at least one coupling rod that is also referred to as a Cardan shaft. The pump has a intake housing as well as a connector, and the stator is connected with one of its ends to a connecting flange of the intake housing and at its other end to a connecting flange of the connector. In the context of the invention, “elastic material” refers particularly to an elastomer, for example a (synthetic) rubber or a rubber mixture. Composite materials made of an elastomer or of another material, such as metal, for example, are also included. The (elastomeric) stator is preferably formed as an axially split stator composed of at least two stator subshells. In such an eccentric screw pump, the (split) stator can be exchanged separately from the stator casing and, consequently, is not permanently and particularly not integrally connected to the stator casing. It is therefore also possible to exchange the elastomeric stator separately from the stator casing, particularly without the necessity of laboriously breaking down the pump. The stator is preferably composed of two stator half-shells. The stator casing is composed of at least two casing segments, for example three casing segments or four casing segments that form a stator clamp. After all, the stator or the stator subshells rest with sealing end faces against corresponding sealing end faces on the respective housing part (intake housing or connector) or on corresponding adapters.
An eccentric screw pump of the type mentioned at the outset is known, for example, from WO 2009/024279 [U.S. Pat. No. 8,439,659]. The casing segments of the stator casing have end mounting flanges that are connected using clamping means to the connecting flanges of the intake housing or connector or to separate adapters for the purpose of clamping the stator. These clamping means are formed as clamping screw devices that are formed essentially as clamping screws that work radially. The known eccentric screw pump has outstandingly proven its worth. One aspect that is especially advantageous is the fact that the clamping pressure of the stator can be adjusted, thus enabling its operation to be optimized after it becomes worn, for example. Taking this as a point of departure, however, the known measures have potential for development. This is where the invention comes in.
It is the object of the invention to provide an eccentric screw pump of the type described above in which the stator can be reliably reclamped, preferably even under higher loads. To achieve this object, the invention teaches in relation to a generic eccentric screw pump of the type described above that the end casing segments each have at least one clamping flange with first clamping surfaces, and that one or more clamping elements with second clamping surfaces are placed onto the clamping flange or the clamping flanges, with the first clamping surfaces and the second clamping surfaces being formed such and coacting such that the stator casing can be pressed against the stator radially on axial displacement of the clamping elements. The first clamping surfaces and/or the second clamping surfaces are formed as wedges. The clamping elements are then frustoconical, for example with inner frustoconical surfaces. The clamping flanges are correspondingly frustoconical, for example with outer frustoconical surfaces. Preferably, both the first clamping surfaces and the second clamping surfaces are formed as wedges that then optionally abut against one another on a common contact surface. However, the contact between the two clamping surfaces, for example wedges, can also be limited to linear contact.
The invention proceeds in this regard initially from the insight that the possibility of adjusting and clamping, particularly of reclamping the stator, is of special importance. According to the invention, this possibility exists in a fundamentally known manner through the aid of the casing segments that are also referred to as adjusting segments and are designed for the purpose of setting the stator clamping and reclamping the stator and therefore constitute a stator clamp. According to the invention, the clamping of the casing segments is now no longer performed directly by radially oriented set screws, but rather “indirectly” by one or more clamping elements that are displaced axially in order to clamp the stator and exert a radial force against the stator on this axial displacement. The coacting clamping surfaces are provided for this purpose and are especially preferably formed as wedges. Due to the configuration of these clamping surfaces or wedges, a “deflection” of the axial force into a radial clamping force occurs. The displacement of the clamping elements or clamping element can be achieved using conventional actuating elements, such as set screws, for example that then do not act radially, however, but rather along or parallel to the axis. With such actuating elements, the clamping element can be displaced axially and thus generate the radial clamping force. It is advantageous here that the actuating elements, for example set screws, must absorb forces primarily on clamping and hence adjustment. During operation, however, only lesser forces have to be absorbed by the actuating elements, for example set screws, because the forces are absorbed for the most part indirectly or directly by the clamping elements that can be displaced axially. In a first embodiment of the invention, a (continuous) clamping ring with an annular second clamping surface is provided as a clamping element, and this second clamping surface of the clamping ring coacts with the first clamping surfaces of the casing segments. Together with its (inner) wedge, this clamping ring forms a frustoconical ring or encompasses a frustoconical ring. The clamping ring can be displaced axially for clamping using suitable actuating elements, such as set screws, so that radial forces are produced on axial displacement with the aid of the corresponding clamping surfaces, for example wedges. During clamping, the clamping forces are applied with the actuating elements, for example set screws, and during operation of the pump, the great forces that then occur can be absorbed by the annular clamping ring, so that the actuating elements themselves, for example set screws, are unburdened for the most part.
In an alternative, second embodiment, it is possible to use not an annular clamping ring, but several individual clamping segments, in which case the individual clamping segments each have a second clamping surface that coacts with the first clamping surfaces of the casing segments. Such individual casing segments can also be displaced axially using suitable actuating elements and the axial actuating movement converted into a radial clamping force by the clamping surfaces, for example wedges. It is expedient here if the corresponding housing parts of the pump or corresponding adapters that are known in principle from the prior art are equipped with suitable holders for the individual clamping segments. It thus lies within the scope of the invention for the housing parts of the pump or their adapters to have receiving pockets that receive the clamping segments and hold and fix them radially and angularly, so that the clamping segments can be displaced in these pockets along or parallel to the axis.
The overall aim of the invention is, on the one hand, to provide clamping elements, such as a clamping ring or several clamping segments that can be displaced in an axial and/or axially parallel manner, and, on the other hand, to provide actuating elements, so that the “clamping” on the one hand and the “holding” on the other hand are uncoupled during operation, thereby unburdening the actuating elements during operation. This offers the advantage, for example, that even pumps with higher loads and particularly higher operating pressures can be reclamped in the inherently known manner with the aid of casing segments or adjusting segments. Set screws can be used as actuating elements, for example, but they do not act radially directly on the casing segments like in the prior art; instead, they act indirectly on the casing segments via the clamping element and are preferably oriented in the axially parallel direction for this purpose. It lies within the scope of the invention for the two stator ends to each be provided with several set screws. The set screws can be formed as pressure screws or as lag screws. Alternatively, it lies within the scope of the invention to clamp the opposing clamping elements, for example clamping rings, against one another using common clamping rods. However, the invention also includes other embodiments in which it is not set screws or adjusting rods or clamping rods that are used, but clamping or adjusting levers that are connected to the clamping elements, for example the clamping ring. For instance, the two opposing clamping rings can be interconnected and pressed against one another by a suitable lever construction. Alternatively, a rotatable adjusting ring can also be provided as an actuating element; this will be discussed further below.
In another embodiment, the clamping ring can have a multipart design and consist at least of an outer ring and an inner ring, in which case the actuating elements, for example set screws, act on the outer ring and the clamping surfaces, for example wedges, are arranged on the inner ring that is then formed as a frustoconical ring. In this regard, the invention proceeds from the insight that it is expedient if the clamping ring has a multipart design consisting of different materials, it being possible for the outer ring to be made of steel or also of cast steel, for example, and for the inner ring to be made of a corrosion-resistant material having good sliding properties, such as brass. This two-part configuration enables optimal adaptation of the materials.
Alternatively, it lies within the scope of the invention for the clamp to have at least one separate clamping subassembly that has a double wedge ring having the second clamping surfaces and enclosing the casing segments, as well as two clamping rings that can be pressed against one another and have the first clamping surfaces. As a result, in this embodiment, the clamping flanges with the clamping surfaces (wedges) are not permanently connected to the respective casing segments, but rather a separate component, namely the double wedge ring, is made available with the first clamping surfaces, it being possible for this double wedge ring to also be replaced by several individual double wedge segments, in which case a double wedge segment is then especially preferably associated with each casing segment.
The clamping is then performed with two clamping rings that can be pressed against one another, with these clamping rings being pressed against one another through the interposition of the double wedge segments or of a double wedge ring. The wedge principle according to the invention is put into practice here as well; after all, the double wedge segments pressed against one another on axial displacement of the two clamping rings radially and consequently pressed against the casing segments. The described advantages according to the invention can be achieved in this way as well.
If set screws are used as actuating elements, it can be expedient if these set screws are oriented (exactly) parallel to the axis. Alternatively, however, it also lies within the scope of the invention to arrange the set screws obliquely, especially preferably parallel or substantially parallel to the first wedges and second wedges. The set screws thus act parallel to the direction of motion of the components on clamping.
In a modified embodiment, it is proposed that the clamping ring be held in a rotating manner and displaced axially and automatically on rotation. This can be achieved, for example, by guiding the clamping ring over a threaded connection on the corresponding housing part or connection adapter, for example by providing the housing part or connection adapter with an outer thread and the clamping ring with the corresponding inner thread. During rotation of the clamping ring on the housing part, the latter is then displaced axially simultaneously toward a closed position. In such an embodiment, it can be expedient to provide the rotatable clamping ring on its outer periphery with teeth so that a corresponding drive can engage therein, for example. Another embodiment of the invention is that a rotatable adjusting ring or a rotatable adjusting ring assembly that effects an axial displacement of the clamping ring or of the clamping segments on rotation is provided as an actuating element. Consequently, in this embodiment, set screws or the like do not act directly on the clamping ring for the displacement; instead, a separate rotatable adjusting ring is provided that produces an axial displacement of the clamping ring on rotation. Here, though, it is not the clamping ring itself that is rotated—as is the case in the embodiment discussed previously—but rather the adjusting ring. As explained in connection with the clamping ring, the adjusting ring can be arranged via a threaded connection on the housing part, so that the adjusting ring is displaced axially on rotation, thereby also axially displacing the clamping ring.
Alternatively, the possibility exists of the adjusting ring being rotatable on the housing part but not itself being displaced axially, but rather with only the clamping ring being displaced axially. This can be achieved, for example, if the adjusting ring has one or more angled faces or oblique support surfaces on the surface facing toward the clamping ring, and/or if the clamping ring has angled faces or oblique support surfaces (corresponding) to the adjusting ring, so that the “total thickness” of adjusting ring on the one hand and clamping ring on the other hand based on the optionally corresponding angled faces changes on rotation, so that the clamping ring is displaced axially.
One embodiment with a rotatable adjusting ring can also be formed such that the adjusting ring and/or the clamping ring is provided with recesses that are formed as guides for rolling and/or sliding bodies, in which case recesses such as rolling bodies, for example (balls, cylinders, or the like) are guided in these recesses, and these rolling and/or sliding bodies act on or press against the clamping element, for example the clamping ring. These guides or recesses extend arcuately along the annular direction over a certain annular or angular range of the adjusting ring and/or clamping ring. They are formed such that the rolling and/or sliding bodies are guided along in the recess on rotation of the adjusting ring angularly, moving in the axial or axially parallel direction and thus actuating the clamping ring axially. For this purpose, recesses can either be provided only in the adjusting ring or only in the clamping ring, or corresponding recesses can be preferably provided both in the adjusting ring and in the clamping ring. In the latter case, the rolling and/or sliding bodies are then guided in the corresponding recesses both of the adjusting ring and of the clamping ring. The recesses can have a tapering width over their length (i.e. angularly of the ring), so that, if balls are used, for example, the balls migrate in these wedge-shaped, tapering recesses during the rotation of the adjusting ring and are pressed out of the recesses. The balls thus move axially on rotation, thereby actuating the clamping ring axially. Especially preferably, however, the recesses are formed as pocket-like, arcuate grooves having a groove depth that decreases from one end to the other. It is expedient if, as a result, it is not (only) that the width of the groove tapers, but the groove rises, so that the rolling and/or sliding body is not guided on the edges but rather rests on the rising base of the groove. In any case, this embodiment with guides and corresponding guide bodies (rolling and/or sliding bodies) also ensures that the “total thickness” of adjusting ring on the one hand and clamping ring on the other hand will change on rotation of the adjusting ring, thereby displacing the clamping ring axially.
Furthermore, it lies within the scope of the invention to manually actuate the actuating elements for actuating the clamping ring for adjusting and reclamping, for example by actuating set screws or the like with suitable tools.
In one possible development, it is proposed that the stator clamp additionally comprises one or more actuators that act so as to automatically advance the actuating elements.
The invention places emphasis primarily on the configuration with the clamping elements with corresponding clamping surfaces, for example wedges. In addition, it is advantageous if locking fittings, for example projections or recesses, are arranged on the clamping flanges of the casing segments that prevent rotation and/or axial movement by coacting with corresponding locking fittings, for example recesses or projections, on a housing part of the pump or on separate adapters. For this purpose, T-shaped projections can be connected to these casing segment projections, for example, that engage in corresponding recesses on the respective housing part or adapter, for example T-section grooves, so that the casing segments on the housing parts or adapters are secured against twisting and against axial movement. Nonetheless, movements of the casing segments radially for clamping are permitted. These locking fittings can be molded directly and integrally on the casing segments or molded into the housing part or adapter. Alternatively, however, it also lies within the scope of the invention to attach such projections to the casing segment or on the housing part or adapter as separate components.